Rationale
Measurement of greenhouse gas (GHG) concentrations and isotopic compositions in the atmosphere is a valuable tool for predicting their sources and sinks, and ultimately how they affect ...Earth's climate. Easy access to unmanned aerial vehicles (UAVs) has opened up new opportunities for remote gas sampling and provides logistical and economic opportunities to improve GHG measurements.
Methods
This study presents synchronized gas chromatography/isotope ratio mass spectrometry (GC/IRMS) methods for the analysis of atmospheric gas samples (20‐mL glass vessels) to determine the stable isotope ratios and concentrations of CO2, CH4 and N2O. To our knowledge there is no comprehensive GC/IRMS setup for successive measurement of CO2, CH4 and N2O analysis meshed with a UAV‐based sampling system. The systems were built using off‐the‐shelf instruments augmented with minor modifications.
Results
The precision of working gas standards achieved for δ13C and δ18O values of CO2 was 0.2‰ and 0.3‰, respectively. The mid‐term precision for δ13C and δ15N values of CH4 and N2O working gas standards was 0.4‰ and 0.3‰, respectively. Injection quantities of working gas standards indicated a relative standard deviation of 1%, 5% and 5% for CO2, CH4 and N2O, respectively. Measurements of atmospheric air samples demonstrated a standard deviation of 0.3‰ and 0.4‰ for the δ13C and δ18O values, respectively, of CO2, 0.5‰ for the δ13C value of CH4 and 0.3‰ for the δ15N value of N2O.
Conclusions
Results from internal calibration and field sample analysis, as well as comparisons with similar measurement techniques, suggest that the method is applicable for the stable isotope analysis of these three important GHGs. In contrast to previously reported findings, the presented method enables successive analysis of all three GHGs from a single ambient atmospheric gas sample.
Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes ...fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N) cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem) in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50-80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers) and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies.
Measurement of greenhouse gas (GHG) concentrations and isotopic compositions in the atmosphere is a valuable tool for predicting their sources and sinks, and ultimately how they affect Earth's ...climate. Easy access to unmanned aerial vehicles (UAVs) has opened up new opportunities for remote gas sampling and provides logistical and economic opportunities to improve GHG measurements.
This study presents synchronized gas chromatography/isotope ratio mass spectrometry (GC/IRMS) methods for the analysis of atmospheric gas samples (20-mL glass vessels) to determine the stable isotope ratios and concentrations of CO
, CH
and N
O. To our knowledge there is no comprehensive GC/IRMS setup for successive measurement of CO
, CH
and N
O analysis meshed with a UAV-based sampling system. The systems were built using off-the-shelf instruments augmented with minor modifications.
The precision of working gas standards achieved for δ
C and δ
O values of CO
was 0.2‰ and 0.3‰, respectively. The mid-term precision for δ
C and δ
N values of CH
and N
O working gas standards was 0.4‰ and 0.3‰, respectively. Injection quantities of working gas standards indicated a relative standard deviation of 1%, 5% and 5% for CO
, CH
and N
O, respectively. Measurements of atmospheric air samples demonstrated a standard deviation of 0.3‰ and 0.4‰ for the δ
C and δ
O values, respectively, of CO
, 0.5‰ for the δ
C value of CH
and 0.3‰ for the δ
N value of N
O.
Results from internal calibration and field sample analysis, as well as comparisons with similar measurement techniques, suggest that the method is applicable for the stable isotope analysis of these three important GHGs. In contrast to previously reported findings, the presented method enables successive analysis of all three GHGs from a single ambient atmospheric gas sample.
Rationale
A silver phosphate reference material (Ag3PO4) for the measurement of stable oxygen isotope compositions is much needed; however, it is not available from the authorities distributing ...reference materials. This study aims to fill this gap by calibrating a new Ag3PO4 stable isotope comparison material produced by the University of Natural Resources and Life Sciences (BOKU).
Methods
Aliquots of Ag3PO4 were distributed to four laboratories who frequently measure the δ18O value in Ag3PO4; the University of Natural Resources and Life Sciences (BOKU), the University of Western Australia (UWA), the University of Helsinki (UH), and the Helmholtz Centre for Environmental Research (UFZ). The instruments used to perform the measurements were high‐temperature conversion elemental analysers coupled with continuous flow isotope ratio mass spectrometers. The working gas δ18O value was set to 0‰ and the normalization was done by a three‐point linear regression using the reference materials IAEA‐601, IAEA‐602, and NBS127.
Results
The mean δ18O value of the new BOKU Ag3PO4 comparison material on the VSMOW‐SLAP scale is 13.71‰ and the combined uncertainty is estimated as ±0.34‰. This estimated uncertainty is within the range typical for comparison materials of phosphates and sulphates. Consistent results from the different laboratories probably derived from similar instrumentation, and use of the same reference materials and normalization procedure. The matrix effect of the different reference materials used in this study was deemed negligible.
Conclusions
The BOKU Ag3PO4 can be used as an alternative comparison material for stable oxygen isotope analysis and is available for stable isotope research laboratories to facilitate calibration.
Cassava production faces challenges in a changing climate. Pulse labelling cassava with
C-CO
has the potential to elucidate carbon allocation mechanisms of cassava under drought stress and with ...potassium application. Understanding these mechanisms could guide efforts to mitigate effects of drought in cassava cropping systems.
Forty-eight cassava plants received a nutrient solution high or low in potassium. Water deficit was imposed on half of the plants at bulk root initiation stage, after which they were labelled for 8 h with
C-CO
in a 15 m
growth chamber. Plants were harvested 8 h, 9 days and 24 days after labelling, and separated into leaves, stems and roots. δ
C values of the different parts were measured using an isotope ratio mass spectrometer, from which
C excess was calculated.
Water deficit decreased transpiration (P < 0.001) and increased carbon respiration (P < 0.05). Potassium application increased assimilate distribution to the roots (P < 0.05) at 9 days after labelling, more strongly for plants under water deficit. The opposite was found at 24 days (P < 0.05) with the legacy of water deficit additionally increasing assimilate distribution to roots (P < 0.05). Youngest, fully expanded leaves contained up to 47% of initial
C excess at 24 days after labelling.
Pulse labelling proved to be successful in shedding light on carbon allocation in relation to water and potassium availability. This technique, once adapted to field conditions, could further be used to improve fertilizer recommendations or change agronomic practices to cope with plant stress.
A silver phosphate reference material (Ag
PO
) for the measurement of stable oxygen isotope compositions is much needed; however, it is not available from the authorities distributing reference ...materials. This study aims to fill this gap by calibrating a new Ag
PO
stable isotope comparison material produced by the University of Natural Resources and Life Sciences (BOKU).
Aliquots of Ag
PO
were distributed to four laboratories who frequently measure the δ
O value in Ag
PO
; the University of Natural Resources and Life Sciences (BOKU), the University of Western Australia (UWA), the University of Helsinki (UH), and the Helmholtz Centre for Environmental Research (UFZ). The instruments used to perform the measurements were high-temperature conversion elemental analysers coupled with continuous flow isotope ratio mass spectrometers. The working gas δ
O value was set to 0‰ and the normalization was done by a three-point linear regression using the reference materials IAEA-601, IAEA-602, and NBS127.
The mean δ
O value of the new BOKU Ag
PO
comparison material on the VSMOW-SLAP scale is 13.71‰ and the combined uncertainty is estimated as ±0.34‰. This estimated uncertainty is within the range typical for comparison materials of phosphates and sulphates. Consistent results from the different laboratories probably derived from similar instrumentation, and use of the same reference materials and normalization procedure. The matrix effect of the different reference materials used in this study was deemed negligible.
The BOKU Ag
PO
can be used as an alternative comparison material for stable oxygen isotope analysis and is available for stable isotope research laboratories to facilitate calibration.
Increasing organic matter/carbon contents of soils is one option proposed to offset climate change inducing greenhouse gas (GHG) emissions, under the auspices of the UNFCC Paris Agreement. One of the ...complementary practices to sequester carbon in soils on decadal time scales is amending it with biochar, a carbon rich byproduct of biomass gasification. In sub-Saharan Africa (SSA), there is a widespread and close interplay of agrarian-based economies and the use of biomass for fuel, which makes the co-benefits of biochar production for agriculture and energy supply explicitly different from the rest of the world. To date, the quantities of residues available from staple crops for biochar production, and their potential for carbon sequestration in farming systems of SSA have not been comprehensively investigated. We assessed the productivity and usage of biomass waste from maize, sorghum, rice, millet, and groundnut crops; specifically quantifying straw, shanks, chaff, and shells, based on measurements from multiple farmer fields and household surveys in eastern Uganda. Moreover, allometric models were tested, using grain productivity, plant height, and density as predictors. These models enable rapid and low-cost assessment of the potential availability of feedstocks at various spatial scales: individual cropland, farm enterprise, region, and country. Ultimately, we modeled the carbon balance in soils of major cropping systems when amended with biochar from biomass residues, and up-scaled this for basic scenario analysis. This interdisciplinary approach showcases that there is significant biophysical potential for soil carbon sequestration in farming systems of Uganda through amendment of biochar derived from unused residues of cereals and legume crops. Furthermore, information about these biomass waste flows is used for estimating the rates of biochar input that could be made to farmlands, as well as the amounts of energy that could be produced with gasifier appliances.
At first glance, there appears little to link nitrogen cycling with entomology other that the use of isotope techniques. Soil management requires a contextual, adaptive, flexible approach that is ...based on understanding the factors that regulate the soil’s fundamental processes. Using stable isotope techniques for the analysis of the inherent biogeochemical processes can explain the complex soil–plant interactions, the determining factors of the nitrogen cycle, and the impacts of applying external inputs. Using the same stable isotope tools enables an interdisciplinary collaboration between soil science and entomology. Emerging plant pests, for instance, non-native insect species, are a threat to the agroecosystems. The knowledge of the origin and movement of invasive insects by using the intrinsic stable isotope signatures embedded in the environment allows identification of entry pathways and thus the establishment of effective management strategies to reduce the potential crop damage. Moreover, the feeding and mating biology of insects can also be understood using isotope techniques. Finally, the movement of mosquitoes can be understood by isotopic labeling so that these dangerous disease vectors can be more effectively managed. This and further research has led to a fuller understanding of insect feeding ecology and leading neatly around to how insect nutrition impacts soil organic matter turnover.
This is an eclectic review and analysis of contemporary and promising stable isotope methodologies to study the biology and ecology of arthropods. It is augmented with literature from other ...disciplines, indicative of the potential for knowledge transfer. It is demonstrated that stable isotopes can be used to understand fundamental processes in the biology and ecology of arthropods, which range from nutrition and resource allocation to dispersal, food-web structure, predation, etc. It is concluded that falling costs and reduced complexity of isotope analysis, besides the emergence of new analytical methods, are likely to improve access to isotope technology for arthropod studies still further. Stable isotopes pose no environmental threat and do not change the chemistry or biology of the target organism or system. These therefore represent ideal tracers for field and ecophysiological studies, thereby avoiding reductionist experimentation and encouraging more holistic approaches. Considering (i) the ease with which insects and other arthropods can be marked, (ii) minimal impact of the label on their behaviour, physiology, and ecology, and (iii) environmental safety, we advocate more widespread application of stable isotope technology in arthropod studies and present a variety of potential uses.
The spread of invasive insect species causes enormous ecological damage and economic losses worldwide. A reliable method that tracks back an invaded insect's origin would be of great use to ...entomologists, phytopathologists, and pest managers. The spongy moth (Lymantria dispar, Linnaeus 1758) is a persistent invasive pest in the Northeastern United States and periodically causes major defoliations in temperate forests. We analyzed field‐captured (Europe, Asia, United States) and laboratory‐reared L. dispar specimens for their natal isotopic hydrogen and nitrogen signatures imprinted in their biological tissues (δ2H and δ15N) and compared these values to the long‐term mean δ2H of regional precipitation (Global Network of Isotopes in Precipitation) and δ15N of regional plants at the capture site. We established the percentage of hydrogen–deuterium exchange for L. dispar tissue (Pex = 8.2%) using the comparative equilibration method and two‐source mixing models, which allowed the extraction of the moth's natal δ2H value. We confirmed that the natal δ2H and δ15N values of our specimens are related to the environmental signatures at their geographic origins. With our regression models, we were able to isolate potentially invasive individuals and give estimations of their geographic origin. To enable the application of these methods on eggs, we established an egg‐to‐adult fraction factor for L. dispar (Δegg‐adult = 16.3 ± 4.3‰). Our models suggested that around 25% of the field‐captured spongy moths worldwide were not native in the investigated capture sites. East Asia was the most frequently identified location of probable origin. Furthermore, our data suggested that eggs found on cargo ships in the United States harbors in Alaska, California, and Louisiana most probably originated from Asian L. dispar in East Russia. These findings show that stable isotope biomarkers give a unique insight into invasive insect species pathways, and thus, can be an effective tool to monitor the spread of insect pest epidemics.
To help slow the spread of invasive insects that cause ecological and economic burdens worldwide, we investigated a reliable method to track back an invaded insect’s natal origin. We confirmed that the natal isotopic values of spongy moths were related to the environmental signatures at their geographic origins. Through regression analysis, estimations of the geographic origin of potentially invasive individuals were possible.
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